From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from dggsgout11.his.huawei.com (dggsgout11.his.huawei.com [45.249.212.51]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 039B66FC5; Tue, 13 Aug 2024 01:35:09 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=45.249.212.51 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1723512913; cv=none; b=Pj29Z6YHLy8L0VKisEWQebnWs9LkNYIzOOce7Enw+YfxqNnIqRTjdpklMZ2A9q5Wh/oSPXaCL/h4414V120n7u9pWXi65qvrfbRlzehE6uJMl6RawA8qf4RiWxauw1b4uS9MpDqR3Suoeuw708ED/1Z633cuy2jcMLrCCYtvgnQ= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1723512913; c=relaxed/simple; bh=vq5JGnkPBY+PGy9/5tulWVSiltIbGn5LlSF/PLadaD0=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=bgYMVWtO6mf48VIT3BugwZ/YVelVy3ZKKFqCz4aCfszdpMODqX0DGDGe7envCQn+9vAvH0d6AyrwLK8Bv+f5hbDoWKPNOZJXhWT7KNB4nN907Rv69M5yWJYBnw7zgpLPkLVTP9sQ63jHbpuWokCzDR8yiCRM0dYX8ANxDv/TTdk= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=huaweicloud.com; spf=pass smtp.mailfrom=huaweicloud.com; arc=none smtp.client-ip=45.249.212.51 Authentication-Results: smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=huaweicloud.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=huaweicloud.com Received: from mail.maildlp.com (unknown [172.19.163.216]) by dggsgout11.his.huawei.com (SkyGuard) with ESMTP id 4WjYpg4MRmz4f3kv7; Tue, 13 Aug 2024 09:34:51 +0800 (CST) Received: from mail02.huawei.com (unknown [10.116.40.75]) by mail.maildlp.com (Postfix) with ESMTP id 41C041A1795; Tue, 13 Aug 2024 09:35:06 +0800 (CST) Received: from [10.67.110.112] (unknown [10.67.110.112]) by APP2 (Coremail) with SMTP id Syh0CgCHvr1IuLpmn38gBg--.32573S2; Tue, 13 Aug 2024 09:35:06 +0800 (CST) Message-ID: <557dea21-c119-4fbf-90f7-fe755b56f6ef@huaweicloud.com> Date: Tue, 13 Aug 2024 09:35:04 +0800 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:102.0) Gecko/20100101 Thunderbird/102.5.1 Subject: Re: [PATCH -next 2/2] cgroup: Disallow delegatee to write all interfaces outsize of cgroup ns Content-Language: en-US To: Chen Ridong , tj@kernel.org, lizefan.x@bytedance.com, hannes@cmpxchg.org, longman@redhat.com, mkoutny@suse.com Cc: cgroups@vger.kernel.org, linux-kernel@vger.kernel.org References: <20240812073746.3070616-1-chenridong@huawei.com> <20240812073746.3070616-3-chenridong@huawei.com> From: Xiu Jianfeng In-Reply-To: <20240812073746.3070616-3-chenridong@huawei.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-CM-TRANSID:Syh0CgCHvr1IuLpmn38gBg--.32573S2 X-Coremail-Antispam: 1UD129KBjvJXoW7tFyxZFyrKw4rWr43ArWrKrg_yoW8Kw1DpF WvyryxJ398Xrn8AF4Yqay0gw4fWFs3XF1UtayDW3yxJr1agr18Kryjk343Xa1UZF4xCryj vFZ0yrWjkr1UtwUanT9S1TB71UUUUU7qnTZGkaVYY2UrUUUUjbIjqfuFe4nvWSU5nxnvy2 9KBjDU0xBIdaVrnRJUUUkEb4IE77IF4wAFF20E14v26r4j6ryUM7CY07I20VC2zVCF04k2 6cxKx2IYs7xG6rWj6s0DM7CIcVAFz4kK6r1j6r18M28lY4IEw2IIxxk0rwA2F7IY1VAKz4 vEj48ve4kI8wA2z4x0Y4vE2Ix0cI8IcVAFwI0_Ar0_tr1l84ACjcxK6xIIjxv20xvEc7Cj xVAFwI0_Gr1j6F4UJwA2z4x0Y4vEx4A2jsIE14v26rxl6s0DM28EF7xvwVC2z280aVCY1x 0267AKxVW0oVCq3wAS0I0E0xvYzxvE52x082IY62kv0487Mc02F40EFcxC0VAKzVAqx4xG 6I80ewAv7VC0I7IYx2IY67AKxVWUJVWUGwAv7VC2z280aVAFwI0_Jr0_Gr1lOx8S6xCaFV Cjc4AY6r1j6r4UM4x0Y48IcVAKI48JMxk0xIA0c2IEe2xFo4CEbIxvr21lc7CjxVAaw2AF wI0_JF0_Jw1l42xK82IYc2Ij64vIr41l4I8I3I0E4IkC6x0Yz7v_Jr0_Gr1lx2IqxVAqx4 xG67AKxVWUJVWUGwC20s026x8GjcxK67AKxVWUGVWUWwC2zVAF1VAY17CE14v26r1q6r43 MIIYrxkI7VAKI48JMIIF0xvE2Ix0cI8IcVAFwI0_Jr0_JF4lIxAIcVC0I7IYx2IY6xkF7I 0E14v26r1j6r4UMIIF0xvE42xK8VAvwI8IcIk0rVWUJVWUCwCI42IY6I8E87Iv67AKxVWU JVW8JwCI42IY6I8E87Iv6xkF7I0E14v26r1j6r4UYxBIdaVFxhVjvjDU0xZFpf9x07UK2N tUUUUU= X-CM-SenderInfo: x0lxyxpdqiv03j6k3tpzhluzxrxghudrp/ On 2024/8/12 15:37, Chen Ridong wrote: > The delegatee shouldn't be allowed to write to the resource control > interface files. The kernel rejects writes to all files other than > "cgroup.procs", "cgroup.threads" and "cgroup.subtree_control" on a > namespace root from inside the namespace. However, delegatee can write > "cgroup.subtree_control" outsize of the namespace, this can be reproduced > by as follows: > > cd /sys/fs/cgroup > echo '+pids' > cgroup.subtree_control > mkdir dlgt_grp_ns > echo '+pids' > dlgt_grp_ns/cgroup.subtree_control > mkdir dlgt_grp_ns/dlgt_grp_ns1 > echo $$ > dlgt_grp_ns/dlgt_grp_ns1/cgroup.procs > echo 200 > dlgt_grp_ns/dlgt_grp_ns1/pids.max > unshare -Cm /bin/bash > echo max > dlgt_grp_ns/dlgt_grp_ns1/pids.max // Permission denied > echo -pids > dlgt_grp_ns/cgroup.subtree_control // pids was unlimited now > > We set pids.max to 200 in the cgroup dlgt_grp_ns1, and we created a new > cgroup namespace. The delegatee can't write to > dlgt_grp_ns/dlgt_grp_ns1/pids.max. However, delegatee can write to > dlgt_grp_ns/cgroup.subtree_control, which is outside of the cgroup > namespace, and this invalided the pids limitation. > > Cgroup namespaces, as delegation boundaries, should disallow the delegatee > to write all interfaces outside of the cgroup namespace. > > Fixes: 5136f6365ce3 ("cgroup: implement "nsdelegate" mount option") > Signed-off-by: Chen Ridong > --- > kernel/cgroup/cgroup.c | 6 ++++-- > 1 file changed, 4 insertions(+), 2 deletions(-) > > diff --git a/kernel/cgroup/cgroup.c b/kernel/cgroup/cgroup.c > index 8dbe00000fd4..1ef9413c02e3 100644 > --- a/kernel/cgroup/cgroup.c > +++ b/kernel/cgroup/cgroup.c > @@ -4134,8 +4134,10 @@ static ssize_t cgroup_file_write(struct kernfs_open_file *of, char *buf, > * cgroup.procs, cgroup.threads and cgroup.subtree_control. > */ > if ((cgrp->root->flags & CGRP_ROOT_NS_DELEGATE) && > - !(cft->flags & CFTYPE_NS_DELEGATABLE) && > - ctx->ns != &init_cgroup_ns && ctx->ns->root_cset->dfl_cgrp == cgrp) > + ctx->ns != &init_cgroup_ns && > + (!cgroup_is_descendant(cgrp, ctx->ns->root_cset->dfl_cgrp) || > + (!(cft->flags & CFTYPE_NS_DELEGATABLE) && > + ctx->ns->root_cset->dfl_cgrp == cgrp))) Can you please match the indentation? Thanks. > return -EPERM; > > if (cft->write)